Liquid dosage forms of sodium naproxen

ABSTRACT

Described herein are oral pharmaceutical compositions comprising liquid dosage forms of sodium naproxen in soft gel capsules. In one embodiment, the pharmaceutical composition comprises sodium naproxen, 0.2-1.0 mole equivalents of a de-ionizing agent per mole of naproxen, polyethylene glycol, and one or more solubilizers such as propylene glycol, polyvinyl pyrrolidone or a combination thereof.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No. 15/591,512, filed on May 10, 2017, which is a continuation of U.S. patent application Ser. No. 14/977,808, filed on Dec. 22, 2015, now U.S. Pat. No. 9,693,978, which is continuation of U.S. patent application Ser. No. 11/367,238, filed Mar. 3, 2006, now abandoned, which claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Patent Application No. 60/659,679, filed Mar. 8, 2005, each of which is incorporated herein in its entirety by express reference thereto.

TECHNICAL FIELD

This application describes liquid dosage forms of sodium naproxen in soft gelatin capsules.

BACKGROUND

Filled one-piece soft gelatin capsules (“softgels”) have been widely used for years to encapsulate consumable materials such as vitamins and pharmaceuticals in a liquid vehicle or carrier. Because softgels have properties which are quite different from two-piece hardshell capsules, softgels are more capable of retaining a liquid fill material.

Not all liquids may be enclosed in a softgel capsule. Liquids containing more than about 20% water by weight are generally not enclosed in softgels, because the water tends to dissolve the gelatin shell. Other solvents such as propylene glycol, glycerin, low molecular weight alcohols, ketones, acids, amines, and esters all tend to degrade or dissolve the gelatin shell to some extent.

Softgels are also somewhat sensitive to pH, and generally require a pH in the encapsulated liquid from about 2.5 to about 7.5. Highly acidic liquids may hydrolyze the gelatin, resulting in leaks, while basic liquids may tan the gelatin, resulting in decreased solubility of the gelatin shell.

Pharmaceutical liquids are usually enclosed in softgels as either viscous solutions or suspensions. Suspensions are pharmaceutically less desirable because they can settle during manufacture, which leads to a less uniform product. In contrast, solutions provide the best liquid form for obtaining optimal “content uniformity” in a batch. Further, solutions typically provide a faster and more uniform absorption of an active agent than do suspensions.

Suitable softgel solutions, however, can be difficult to achieve. One constraint is size. Many pharmaceutical agents require volumes of solvent too large to produce a softgel capsule small enough to be taken by patients. The solvent must also have sufficient solvating power to dissolve a large amount of the pharmaceutical agent to produce a concentrated solution and yet not dissolve, hydrolyze or tan the gelatin shell.

Concentrated solutions of pharmaceutical agents for use in softgel capsules have been described. Most of these systems involve ionizing the free pharmaceutical agent in situ to the corresponding salt. For example, U.S. Pat. No. 5,360,615 to Yu et al. discloses a solvent system for enhancing the solubility of acidic, basic, or amphoteric pharmaceutical agents. The solvent system comprises polyethylene glycol, an ionizing agent, and water. The ionizing agent functions by causing the partial ionization of the free pharmaceutical agent. U.S. Pat. No. 6,383,515, U.S. Patent Application Publication No. 2002/0187195, and U.S. Patent Application Publication No. 2001/0007668 to Sawyer et al. discloses pharmaceutically acceptable solutions containing a medicament suitable for filling softgel capsules comprising a polymer such as polyethylene glycol and an acid salt of a compound having three or more carbon atoms, such as sodium propionate. The salt helps to ionize the medicament without relying on the use of strong acids or bases. U.S. Pat. No. 6,689,382 to Berthel et al. describes a pharmaceutical formulation suitable for filling softgel capsules comprising (a) a therapeutically effective amount of a non-steroidal anti-inflammatory drug (NSAID); and (b) a solvent system comprising 40% to 60% by weight a polyoxyethylene ether, 15% to 35% by weight of glycerin and 15% to 35% by weight water. In cases where the NSAID has a carboxyl or an acidic functional group, the solvent system also includes hydroxide ions. U.S. Pat. No. 5,505,961 to Shelley et al. describes a method for increasing the solubility of acetaminophen alone or in combination with other pharmaceutically active agents to form a clear solution for encapsulation into a softgel capsule. The method comprises solubilizing acetaminophen in a mixture of propylene glycol, polyethylene glycol, water, polyvinylpyrrolidone and sodium or potassium acetate.

The previously described methods all involve the conversion of the free pharmaceutical agent to the corresponding salt. In cases where the free pharmaceutical agent is acidic, the resulting anion can react with the polyethylene glycol in the fill to produce polyethylene glycol esters, thus reducing the amount of available pharmaceutical agent.

There is a need for a solvent system containing a medicament, which can be encapsulated in a softgel capsule, wherein the formation of PEG esters is minimized.

Therefore, it is an object of the invention to provide a stable solvent system for pharmaceutical agents, which is suitable for encapsulation in a softgel capsule, wherein the formation of PEG esters is minimized.

SUMMARY

Liquid and semi-solid pharmaceutical compositions, which can be administered in liquid form or can be used for preparing capsules, are described herein. The composition comprises the salt of one or more active agents, such as naproxen, and 0.2-1.0 mole equivalents of a de-ionizing agent per mole of active agent. The pH of the composition is adjusted within the range of 2.5-7.5. The de-ionizing agent causes partial de-ionization (neutralization) of the salt of the active agent resulting in enhanced bioavailability of salts of weakly acidic, basic or amphoteric active agents as well as decreased amounts of polyethylene glycol (PEG) esters.

Described herein are oral pharmaceutical compositions comprising liquid dosage forms of sodium naproxen in soft gel capsules. In one embodiment, the pharmaceutical composition comprises sodium naproxen, 0.2-1.0 mole equivalents of a de-ionizing agent per mole of naproxen, polyethylene glycol, and one or more solubilizers such as propylene glycol, polyvinyl pyrrolidone or a combination thereof.

One embodiment described herein is a pharmaceutical composition comprising a soft gel capsule encapsulating a liquid matrix comprising: (a) naproxen sodium; (b) one or more deionizing agents comprising fumaric acid, maleic acid, tartaric acid, citric acid, malic acid, acetic acid, proprionic acid, pyruvic acid, butanoic acid, or lactic acid in an amount of from 0.2 to 1.0 mole equivalents per mole of naproxen sodium; (c) one or more polyethylene glycols; and (d) one or more solubilizers comprising polyvinylpyrrolidone, propylene glycol, or a combination thereof. In one aspect described herein, the deionizing agent comprises citric acid or lactic acid. In another aspect described herein, the deionizing agent comprises lactic acid. In another aspect described herein, the polyethylene glycol comprises from about 10% to about 80% by weight of the composition. In another aspect described herein, the polyethylene glycol comprises one or more polyethylene glycols with a molecular weight between 300 and 1500. In another aspect described herein, the polyethylene glycol comprises polyethylene glycol 600. In another aspect described herein, the solubilizer comprises from about 1% to 10% by weight of the composition. In another aspect described herein, the solubilizer comprises about 2% polyvinylpyrrolidone and about 2% propylene glycol. In another aspect described herein, the composition further comprises one or more excipients comprising plasticizers, crystallization inhibitors, wetting agents, bulk filling agents, solubilizers, bioavailability enhancers, solvents, dyes, preservatives, surfactants, or combinations thereof.

Another embodiment described herein is a pharmaceutical composition comprising: (a) about 25% naproxen sodium by weight; (b) lactic acid in an amount of from about 0.2 to about 1.0 mole equivalents per mole of naproxen sodium; (c) about 10% to about 80% of one or more polyethylene glycols by weight; and (d) about 1% to about 10% by weight of one or more solubilizers comprising polyvinylpyrrolidone, propylene glycol, or a combination thereof. In one aspect described herein, the polyethylene glycol comprises one or more polyethylene glycols with a molecular weight between 300 and 1500. In another aspect described herein, the polyethylene glycol comprises polyethylene glycol 600. In another aspect described herein, the solubilizer comprises propylene glycol and polyvinyl pyrrolidone. In another aspect described herein, the lactic acid comprises about 0.6 mole equivalents per mole of naproxen sodium. In another aspect described herein, the weight percentage of lactic acid is about 5%. In another aspect described herein, the solubilizer comprises about 2% polyvinylpyrrolidone and about 2% propylene glycol. In another aspect described herein, the composition further comprises one or more excipients selected from plasticizers, crystallization inhibitors, wetting agents, bulk filling agents, bioavailability enhancers, solvents, dyes, preservatives, surfactants, or combinations thereof. In another aspect described herein, the pH is from about 2.5 to about 7.5. In another aspect described herein, the composition is encapsulated in a softgel capsule. In another aspect described herein, the softgel capsule comprises: (a) gelatin; (b) plasticizer; and (c) purified water.

Another embodiment described herein is a method for making a pharmaceutical composition, the method comprising: (a) mixing together (i) about 25% naproxen sodium by weight; (ii) lactic acid in an amount of from about 0.2 to about 1.0 mole equivalents per mole of naproxen sodium; (ii) about 10% to about 80% of one or more polyethylene glycols by weight; and (iv) about 1% to about 10% by weight of one or more solubilizers comprising polyvinylpyrrolidone, propylene glycol, or a combination thereof; and (b) encapsulating the mixture in a softgel capsule using rotary die encapsulation.

Another embodiment described herein is an oral dosage form produced by the method described herein.

DETAILED DESCRIPTION

I. Composition

A. Fill Materials

1. Drugs to be Formulated

The formulation can contain any therapeutic, diagnostic, prophylactic or nutraceutical agent. Exemplary agents include, but are not limited to, analeptic agents; analgesic agents; anesthetic agents; antiasthmatic agents; antiarthritic agents; anticancer agents; anticholinergic agents; anticonvulsant agents; antidepressant agents; antidiabetic agents; antidiarrheal agents; antiemetic agents; antihelminthic agents; antihistamines; antihyperlipidemic agents; antihypertensive agents; anti-infective agents; anti-inflammatory agents; antimigraine agents; antineoplastic agents; antiparkinson drugs; antipruritic agents; antipsychotic agents; antipyretic agents; antispasmodic agents; antitubercular agents; antiulcer agents; antiviral agents; anxiolytic agents; appetite suppressants (anorexic agents); attention deficit disorder and attention deficit hyperactivity disorder drugs; cardiovascular agents including calcium channel blockers, antianginal agents, central nervous system (“CNS”) agents, beta-blockers and antiarrhythmic agents; central nervous system stimulants; diuretics; genetic materials; hormonolytics; hypnotics; hypoglycemic agents; immunosuppressive agents; muscle relaxants; narcotic antagonists; nicotine; nutritional agents; parasympatholytics; peptide drugs; psychostimulants; sedatives; sialagogues, steroids; smoking cessation agents; sympathomimetics; tranquilizers; vasodilators; beta-agonist; and tocolytic agents.

A first class of drugs is selected based on inclusion in the molecule of a weakly acidic, basic or amphoteric group that can form a salt. Any drug that bears an acidic or a basic functional group, for example, an amine, imine, imidazoyl, guanidine, piperidinyl, pyridinyl, quaternary ammonium, or other basic group, or a carboxylic, phosphoric, phenolic, sulfuric, sulfonic or other acidic group, can react with the de-ionizing agent.

Some specific drugs that bear acidic or basic functional groups and thus may be converted to the corresponding salt for use in the described formulations include, but are not limited to, Acetaminophen, Acetylsalicylic acid, Alendronic acid, Alosetron, Amantadine, Amlopidine, Anagrelide, Argatroban, Atomoxetine, Atrovastatin, Azithromycin dehydrate, Balsalazide, Bromocriptan, Bupropion, Candesartan, Carboplatin, Ceftriaxone, Clavulonic acid, Clindamycin, Cimetadine, Dehydrocholic (acid), Dexmethylphenidate, Diclofenac, Dicyclomine, Diflunisal, Diltiazem, Donepezil, Doxorubicin, Doxepin, Epirubicin, Etodolic acid, Ethacrynic acid, Fenoprofen, Fluoxetine, Flurbiprofen, Furosemide, Gemfibrozil, Hydroxyzine, Ibuprofen, Imipramine, Indomethacin, Ketoprofen, Levothyroxine, Maprolitline, Meclizine, Methadone, Methylphenidate, Minocycline, Mitoxantone, Moxifloxacin, Mycophenolic acid, Naproxen, Niflumic acid, Ofloxacin, Ondansetron, Pantoprazole, Paroxetine, Pergolide, Pramipexole, Phenytoin, Pravastain, Probenecid, Rabeprazole, Risedronic acid, Retinoic acid, Ropinirole, Selegiline, Sulindac, Tamsulosin, Telmisertan, Terbinafine, Theophyline, Tiludronic Acid, Tinzaparin, Ticarcillin, Tometin, Valproic acid, Salicylic acid, Sevelamer, Ziprasidone, Zoledronic acid, Acetophenazine, Albuterol, Almotriptan, Amitriptyline, Amphetamine, Atracurium, Beclomethasone, Benztropine, Biperiden, Bosentan, Bromodiphenhydramine, Brompheniramine carbinoxamine, Caffeine, Capecitabine, Carbergoline, Cetirizine, Chlocylizine, Chlorpheniramine, Chlorphenoxamine, Chlorpromazine, Citalopram, Clavunate potassium, Ciprofloxacin, Clemastine, Clomiphene, Clonidine, Clopidogrel, Codeine, Cyclizine, Cyclobenzaprine, Cyproheptadine, Delavirdine, Diethylpropion, Divalproex, Desipramine, Dexmethylphenidate, Dexbrompheniramine, Dexchlopheniramine, Dexchlor, Dextroamphetamine, Dexedrine, Dextromethorphan, Fiflunisal, Diphemanil methylsulphate, Diphenhydramine, Dolasetron, Doxylamine, Enoxaparin, Ergotamine, Ertepenem, Eprosartan, Escitalopram, Esomeprazole, Fenoldopam, Fentanyl, Fexofenadine, Flufenamic acid, Fluvastatin, Fluphenazine, Fluticasone, Fosinopril, Frovatriptan, Gabapentin, Galatamine, Gatifloxacin, Gemcitabine, Haloperidol, Hyalurondate, Hydrocodone, Hydroxychloroquine, Hyoscyamine, Imatinib, Imipenem, Ipatropin, Lisinopril, Leuprolide, Levopropoxyphene, Losartan, Meclofenamic acid, Mefanamic acid, Mesalamine, Mepenzolate, Meperidine, Mephentermine, Mesalimine, Mesoridazine, Metaproteranol, Metformin, Methdialazine, Methscopolamine, Methysergide, Metoprolol, Metronidazole, Mibefradil, Montelukast, Morphine, Mometasone, Naratriptan, Nelfinavir, Nortriptylene, Noscapine, Nylindrin, Omeprazole, Orphenadrine, Oseltamivir, Oxybutynin, Papaverine, Pentazocine, Phendimetrazine, Phentermine, Pioglitazone, Pilocarpine, Prochloroperazine, Pyrilamine, Quetapine, Ranitidine, Rivastigmine, Rosiglitazone, Salmetrol, Sertaline, Sotalol, Sumatriptan, Tazobactam, Tacrolimus, Tamoxifen, Ticlopidine, Topiramate, Tolterodine, Triptorelin, Triplennamine, Triprolidine, Tramadol, Trovofloxacin, Ursodiol, Promazine, Propoxyphene, Propanolol, Pseudoephedrine, Pyrilamine, Quinidine, Oxybate sodium, Sermorelin, Tacrolimus, Tegaseroid, Teriparatide, Tolterodine, Triptorelin pamoate, Scoplolamine, Venlafaxine, Zamivir, Aminocaproic acid, Aminosalicylic acid, Hydromorphone, Isosuprine, Levorphanol, Melhalan, Nalidixic acid, and Para-aminosalicylic acid.

2. Deionizing Agent

The deionizing agent functions by causing partial deionization (neutralization) of the salt of one or more pharmaceutically active agents. When the active agent is the salt of a weak acid and a strong base, the deionizing agent is preferably a hydrogen ion species. When the active agent is the salt of a weak base and a strong acid, the deionizing agent is preferably a hydroxide ion species. The deionizing agent is preferably present in an amount between 0.2 to 1.0 mole equivalents per mole of the pharmaceutically active agent.

Exemplary hydrogen ion species useful as de-ionizing agents described herein, include, but are not limited to, hydrochloric acid, hydrobromic acid, hydroiodic acid, sulfuric acid, fumaric acid, maleic acid, tartaric acid, methane-, ethane-, and benzene sulfonates, citric acid, malic acid, acetic acid, proprionic acid, pyruvic acid, butanoic acid, and lactic acid.

Exemplary hydroxide ion species useful as de-ionizing agents described herein, include, but are not limited to, metal hydroxides such as sodium hydroxide, potassium hydroxide, ammonium hydroxide, calcium hydroxide, aluminum hydroxide, and magnesium hydroxide.

Additional acid or base can be added to adjust the pH of the fill composition. In a preferred embodiment, the pH of the fill composition is from about 2.5 to about 7.5.

3. Excipients

Formulations may be prepared using a pharmaceutically acceptable carrier composed of materials that are considered safe and effective and may be administered to an individual without causing undesirable biological side effects or unwanted interactions. The carrier is all components present in the pharmaceutical formulation other than the active ingredient or ingredients. As generally used herein “carrier” includes, but is not limited to, plasticizers, crystallization inhibitors, wetting agents, bulk filling agents, solubilizers, bioavailability enhancers, solvents, pH-adjusting agents and combinations thereof.

In a preferred embodiment, a mixture of polyethylene glycol and water is used as a solvent for the salt of the active agent and the de-ionizing agent. Polyethylene glycol is present in an amount from about 10% to about 80% by weight. Water is present in an amount from about 1% to 18% by weight. The molecular weight of polyethylene glycol is between 300 and 1500. Other suitable solvents include surfactants and copolymers of polyethylene glycol. Optionally, glycerin, polyvinyl pyrrolidone (PVP) or propylene glycol (PPG) can be added to enhance the solubility of the drug agent.

B. Shell Compositions

1. Gelatin

Gelatin is the product of the partial hydrolysis of collagen. Gelatin is classified as either Type A or Type B gelatin. Type A gelatin is derived from the acid hydrolysis of collagen while Type B gelatin is derived from alkaline hydrolysis of collagen. Traditionally, bovine bones and skins have been used as raw materials for manufacturing Type A and Type B gelatin while porcine skins have been used extensively for manufacturing Type A gelatin. In general acid-processed gelatins form stronger gels than lime-processed gelatins of the same average molecular weight.

2. Other Shell Additives

Other suitable shell additives include plasticizers, opacifiers, colorants, humectants, preservatives, flavorings, and buffering salts and acids.

Plasticizers are chemical agents added to gelatin to make the material softer and more flexible. Suitable plasticizers include glycerin, sorbitol solutions which are mixtures of sorbitol and sorbitan, and other polyhydric alcohols such as propylene glycol and maltitol or combinations thereof.

Opacifiers are used to opacify the capsule shell when the encapsulated active agents are light sensitive. Suitable opacifiers include titanium dioxide, zinc oxide, calcium carbonate and combinations thereof.

Colorants can be used to for marketing and product identification/differentiation purposes. Suitable colorants include synthetic and natural dyes and combinations thereof.

Humectants can be used to suppress the water activity of the softgel. Suitable humectants include glycerin and sorbitol, which are often components of the plasticizer composition. Due to the low water activity of dried, properly stored softgels, the greatest risk from microorganisms comes from molds and yeasts. For this reason, preservatives can be incorporated into the capsule shell. Suitable preservatives include alkyl esters of p-hydroxy benzoic acid such as methyl, ethyl, propyl, butyl and heptyl (collectively known as “parabens”) or combinations thereof.

Flavorings can be used to mask unpleasant odors and tastes of fill formulations. Suitable flavorings include synthetic and natural flavorings. The use of flavorings can be problematic due to the presence of aldehydes which can cross-link gelatin. As a result, buffering salts and acids can be used in conjunction with flavorings that contain aldehydes in order to inhibit cross-linking of the gelatin.

II. Methods of Making

A. Fill Material

The fill material is prepared by mixing the agent (such as a salt of the drug), the deionizing agent, water, and polyethylene glycol at a temperature of 50° C. to 70° C. The resulting solution is encapsulated using the appropriate gel mass. The pharmaceutical agent is present in an amount from about 10% to about 50% by weight. The deionizing agent is present in an amount from about 0.2 to 1.0 mole per mole of the pharmaceutical agent. Water is present in an amount from about 1% to about 20% by weight and polyethylene glycol is present in amount from about 10% to about 80% by weight. Optionally, propylene glycol and/or polyvinyl pyrrolidone are present in an amount from about 1% to about 10%.

B. Gel Mass

The main ingredients of the softgel capsule shell are gelatin, plasticizer, and purified water. Typical gel formulations contain (w/w) 40-50% gelatin, 20-30% plasticizer, and 30-40% purified water. Most of the water is subsequently lost during capsule drying. The ingredients are combined to form a molten gelatin mass using either a cold melt or a hot melt process. The prepared gel masses are transferred to preheated, temperature-controlled, jacketed holding tanks where the gel mass is aged at 50-60° C. until used for encapsulation.

1. Cold Melt Process

The cold melt process involves mixing gelatin with plasticizer and chilled water and then transferring the mixture to a jacket-heated tank. Typically, gelatin is added to the plasticizer at ambient temperature (18-22° C.). The mixture is cooked (57-95° C.) under vacuum for 15-30 minutes to a homogeneous, deaerated gel mass. Additional shell additives can be added to the gel mass at any point during the gel manufacturing process or they may be incorporated into the finished gel mass using a high torque mixer.

2. Hot Melt Process

The hot melt process involves adding, under mild agitation, the gelatin to a preheated (60-80° C.) mixture of plasticizer and water and stirring the blend until complete melting is achieved. While the hot melt process is faster than the cold melt process, it is less accurately controlled and more susceptible to foaming and dusting.

C. Softgel Capsule

Softgel capsules are typically produced using a rotary die encapsulation process. The gel mass is fed either by gravity or through positive displacement pumping to two heated (48-65° C.) metering devices. The metering devices control the flow of gel into cooled (10-18° C.), rotating casting drums. Ribbons are formed as the cast gel masses set on contact with the surface of the drums.

The ribbons are fed through a series of guide rolls and between injection wedges and the capsule-forming dies. A food-grade lubricant oil is applied onto the ribbons to reduce their tackiness and facilitate their transfer. Suitable lubricants include mineral oil, medium chain triglycerides, and soybean oil. Fill formulations are fed into the encapsulation machine by gravity. In the preferred embodiment, the softgels contain printing on the surface, optionally identifying the encapsulated agent and/or dosage.

III. Methods of Use

The softgels may be used to encapsulate a wide range of pharmaceutically active agents, nutritional agents, and personal care products. Softgel capsules may be administered orally to a patient to deliver a pharmaceutically active agent.

It is understood that the disclosed invention is not limited to the particular methodology, protocols, and reagents described as these may vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to limit the scope of the present invention which will be limited only by the appended claims.

Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one of skill in the art to which the disclosed invention belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, the preferred methods, devices, and materials are as described. Publications cited herein and the materials for which they are cited are specifically incorporated by reference. Nothing herein is to be construed as an admission that the invention is not entitled to antedate such disclosure by virtue of prior invention.

Examples

In the following examples, the fill material can be prepared by mixing the salt of one or more pharmaceutically active agents, the deionizing agent, water, and polyethylene glycol at a temperature of 50° C. to 70° C. The resulting solution can be encapsulated in a softgel capsule using the appropriate gel mass.

Example 1. Naproxen Sodium with Acetic Acid as the Deionizing Agent Fill Material Ingredients % (by weight) Naproxen Sodium 25.50 Acetic Acid 3.00 PVP 1.85 PEG 400 62.30 Water 7.40 TOTAL 100%

Example 2. Naproxen Sodium with Citric Acid as the Deionizing Agent Fill Material Ingredients % (by weight) Naproxen Sodium 25.50 Citric Acid 4.75 PVP 1.85 PEG 400 60.50 Water 7.40 TOTAL 100%

Example 3 Naproxen Sodium with Hydrochloric Acid as the Deionizing Agent Fill Material Ingredients % (by weight) Naproxen Sodium 25.50 Hydrochloric Acid 4.72 PVP 1.85 PEG 400 63.52 Water 7.40 TOTAL 100%

Example 4. Naproxen Sodium with Acetic Acid as the Deionizing Agent Fill Material Ingredients % (by weight) Naproxen Sodium 25.50 Acetic Acid 3.00 PVP 1.85 PEG 400 31.15 Water 7.40 PEG 600 31.15 TOTAL 100%

Example 5. Naproxen Sodium with Citric Acid as the Deionizing Agent Fill Material Ingredients % (by weight) Naproxen Sodium 25.50 Citric Acid 40.75 PVP 1.85 PEG 400 30.25 Water 7.40 PEG 600 30.25 TOTAL 100%

Example 6. Naproxen Sodium with Hydrochloric Acid as the Deionizing Agent Fill Material Ingredients % (by weight) Naproxen Sodium 25.50 Hydrochloric Acid 40.72 PVP 1.85 PEG 400 30.25 Water 7.40 PEG 600 30.25 TOTAL 100%

Example 7. Naproxen Sodium with Lactic Acid as the Deionizing Agent Fill Material Ingredients % (by weight) Naproxen Sodium 27.50 Lactic Acid 5.27 Propylene Glycol 2.00 PEG 400 64.64 Water 0.60 TOTAL 100%

Example 8. Naproxen Sodium with Lactic Acid as the Deionizing Agent Fill Material Ingredients % (by weight) Naproxen Sodium 25.00 Lactic Acid 0.24-0.35M Propylene Glycol  2.00 PEG 600 q.s. TOTAL 100%

Example 9. Naproxen Sodium with Lactic Acid as the Deionizing Agent Fill Material Ingredients % (by weight) Naproxen Sodium 25.00 Lactic Acid 5.00 Propylene Glycol 2.00 PEG 600 61.20 PEG 1000 6.80 TOTAL 100%

Example 10. Naproxen Sodium with Lactic Acid as the Deionizing Agent Fill Material Ingredients % (by weight) Naproxen Sodium 25.00 Lactic Acid 5.00 Propylene Glycol 2.00 PEG 600 51.00 PEG 1000 17.00 TOTAL 100%

Example 11. Naproxen Sodium with Lactic Acid as the Deionizing Agent Fill Material Ingredients % (by weight) Naproxen Sodium 25.00 Lactic Acid 5.00 Propylene Glycol 2.00 PEG 600 34.00 PEG 1000 34.00 TOTAL 100%

Example 12. Naproxen Sodium with Lactic Acid as the Deionizing Agent Fill Material Ingredients % (by weight) Naproxen Sodium 25.00 Lactic Acid 5.00 Propylene Glycol 2.00 PEG 600 17.00 PEG 1000 51.00 TOTAL 100% 

The invention claimed is:
 1. A soft gelatin capsule comprising a fill material comprising: (a) a naproxen salt; (b) a deionizing agent comprising acetic acid, propionic acid, pyruvic acid, or lactic acid in an amount of from 0.2 to 1.0 mole equivalents per mole of naproxen salt; (c) polyethylene glycol; and (d) one or more solubilizers.
 2. The capsule of claim 1, wherein the naproxen salt is naproxen sodium.
 3. The capsule of claim 1, wherein the fill material further comprises water in an amount from 1% to 18% by weight.
 4. The capsule of claim 1, wherein polyethylene glycol is present in an amount from 10% to 80% by weight.
 5. The capsule of claim 1, wherein the polyethylene glycol comprises one or more polyethylene glycols with a molecular weight between 300 and
 1500. 6. The capsule of claim 1, wherein the solubilizer is present in amount from 1% to 10% by weight.
 7. The capsule of claim 1, wherein the one or more solubilizers comprise glycerin, polyvinylpyrrolidone, propylene glycol, or combinations thereof.
 8. The capsule of claim 1, further comprising one or more excipients comprising plasticizers, crystallization inhibitors, wetting agents, bulk filling agents, bioavailability enhancers, solvents, dyes, preservatives, surfactants, or combinations thereof.
 9. The capsule of claim 1, wherein the fill material is liquid.
 10. A method for treating pain, inflammation, or fever comprising administering the capsule of claim 1 to a patient in need thereof.
 11. A method of making the capsule of claim 1 comprising: (a) mixing components (a), (b), (c), and (d) as defined in claim 1; and (b) encapsulating the mixture in a softgel capsule.
 12. The method of claim 11, wherein step (a) is conducted at a temperature of from 50° C. to 70° C.
 13. A soft gelatin capsule comprising a fill material comprising: (a) naproxen sodium; (b) a deionizing agent comprising acetic acid, propionic acid, pyruvic acid, or lactic acid in an amount of from 0.2 to 1.0 mole equivalents per mole of naproxen sodium; (c) polyethylene glycol; and (d) a solubilizer comprising glycerin, polyvinylpyrrolidone, propylene glycol, or combinations thereof.
 14. The capsule of claim 13, wherein polyethylene glycol is present in an amount from 10% to 80% by weight.
 15. The capsule of claim 13, wherein the polyethylene glycol comprises one or more polyethylene glycols with a molecular weight between 300 and
 1500. 16. The capsule of claim 13, wherein the fill material further comprises water in an amount from 1% to 18% by weight.
 17. The capsule of claim 13, further comprising one or more excipients comprising plasticizers, crystallization inhibitors, wetting agents, bulk filling agents, bioavailability enhancers, solvents, dyes, preservatives, surfactants, or combinations thereof.
 18. The capsule of claim 13, wherein the solubilizer is present in amount from 1% to 10% by weight.
 19. The capsule of claim 13, wherein the fill material is liquid.
 20. A method for treating pain, inflammation, or fever comprising administering the capsule of claim 13 to a patient in need thereof.
 21. The capsule of claim 1, wherein the deionizing agent is lactic acid.
 22. The capsule of claim 13, wherein the deionizing agent is lactic acid. 